Hydraulic system



April 30, 1946. W. R. TUCKER 2,399,520

HYDRAULI C SYSTEM Filed Feb. 9, 1942 2:8 A: I 42 4 WWW NW WMZI Z Z 7 -ZZKQ Jww4amhw ATTORNEYS Patented Apr. 30, 1946 2,399,520 HYDRAULIC SYSTEM Warren H. Tucker, Dayton,

Ohio, assignor to The Hydraulic Development Corporation, Inc.-, Wilmington, Del., a corporation of Delaware Application February 9, 1942; Serial No. 430,040

4 Claims.

This invention relates to hydraulic systems and, in particular, to hydraulic systems comprising fluid operable means cOntroHing a pump, and pilot means for actuating said controlling means.

In hydraulic systems of the above mentioned type, it has been customary heretofore to provide a pilot pump for actuating fluid operable means controlling the movement of the flow control member of a variable delivery pump. Such pilot pumps, which are used only during the brief period of changing the direction of delivery of the main pump; are relatively expensive to manufacture, and, in case of aconstant delivery pilot pump, are also expensive in operationbecause the delivery of such a pilot pump is by-passed to an exhaust during most of the time of its operation. Furthermore, if a variation of the delivery of the pilot pump is desired, the pilot pump has to be constructed as a variable delivery pump, or additional means is necessary in connection with the pilot pump to allow such variation.

Accordingly, it is an object of the invention to provide simplified means which is adapted to replace the pilot pumps heretofore used in systerms of the above mentioned type, while being less expensive than such pilot pumps.

It is another object of the invention to provide a hydraulic system comprisin a variable delivery pump and fluid operable means for varying the delivery thereof, in which accumulator means is provided adapted to supply pressure fluid to said fluid operable means and to be loaded" by said pump.

A further object of the invention consists in the provision of a system of the type mentioned above, in which the accumulator means is provided with simple adjusting means for varying the quantity of fluid delivered by said accumulator means.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, in which:

Figure l diagrammatically illustrates a hydraulic system comprising accumulator means according to the invention.

Figure 2 is a section through an embodiment of accumulator means according to the invention.

Figure 3 is a simplified section through servomotor means of the pump shown in Figure 1.

General arrangement The hydraulic system according to theinverition substantially comprises a variable delivery pump with fluid operable servomotor means for causing movement of the flow control member of the pump and, thereby, variation of the pump delivery, while a cylinder piston assembly is hydraulically connected with said servomotor means and also with the delivery side of the pump.

In this way, the said cylinder piston assembly is loaded by the delivery of the pump and, in case a variation of the delivery or direction of delivery of the pump is desired, delivers fluid to the servomotor means for actuating the same.

Structural arrangement Referring now to the drawing in detail, the hydraulic circuit shown in Figure 1 comprises a press cylinder l0 having recipr'ocably mounted therein a ram, generally designated H, and comprising a piston'I-i' and piston rod 13, which latter'supports the press platen I4.

Mounted on top of the press cylinder I0 is a fluid reservoir 'or surge tank [5 housing a main cylinder release and pump by-pass valve l6 and a surge valve IT. The valve I'B serves the purpose of facilitating the initiation of the retraction stroke of the press ram H by releasing the pressure from the advancing side of said ram, While the surge valve H is intended to allow prefilling of the press cylinder l0 during the first portion of the advancing stroke of the press ram, during which the latter moves downwardly by gravity. The valves l6 and I! do not form a part of the present invention and for a more detailed description thereof, reference may respectively be had to U. S. Patents Nos. 2,268,205 and 2,193,248 both to Ernst.

The surge valve l1 and main cylinder release and pump by-pass valve l6 are interconnected by conduit means l8 and I9, which latter comprises a safety valve 2|] andleads to the lower portion of the press cylinder Ill. The upper portion of the press cylinder I 0 communicates with a conduit 2| comprising a safety valve 22 and leading to the main cylinder release and pump bypass valve I6.

Also communicating with the upper portion of the press cylinder [0 is a conduit 23 comprising a tonnage control valve 24 and leading to the tank I 5. The tonnage control valve 24 may be of any desired type, for instance, of the type disclosed in U. S; Patent 2,224,957 to Ernst. The tonnage control valve 24 is adapted, in response to a predetermined pressure acting upon the advancing side of the piston 12, to break the energizing circuit for the solenoid 25 which, when energized, attracts an armature 26. The armature 2G is connected by a link 2! with a three The lever 28 has its arm 36 connected with a link system 31, which is pivotally connected with a valve member 38 (see Figure 8). The valve member 36 comprises a collar 39 for limiting its leftward movement and a control piston 40. The

control piston 49 is reciprocable in a bore 4| provided in a reciprocable control rod 42 which, in its turn, is connected with the flow control member of the pump 43 in any conventional manner. The pump 43 is a reversible variable delivery pump and for a more detailed description thereof reference may be had to U. S. Patent No. 2,184,665 to Ernst.

Arranged between the control piston 40 and the bottom of the bore 4| is a spring 44 continuously urging the piston 46 toward the left. The reciprocable control rod 42 comprises a differential piston 45 reciprocable in the servomotor casing 46, which latter has a port 41 communicating with an exhaust line 48, which latter leads to the tank I5.

The servomotor casing 46 is also provided with a port 49 communicating with a conduit 50 leading to the conduit The diiierential piston 45 comprises a larger piston portion 52 and a smaller piston portion 53. The smaller piston portion 53 is provided with channels 54 connecting the bore 55 with the bore 4|. The piston portion 53 furthermore comprises passageways 56 communicating through passageways 51 with the left side of the piston portion 52. Passageways 58 are provided in the smaller piston portion 53 adjacent the larger piston portion 52, which passageways are adapted to effect communication between the bore 59, in which the piston portion 52 is reciprocable. with the bore 4|, in which the control piston 40 is slidable.

The conduit 5|, which communicates with the port 49 in the servomotor casing 46 through the conduit 50. has one end connected to the port 66 in the closure member 6| of the accumulator, generally designated 62. The closure member 6| is connected to the cylinder 63 in any convenient manner, for instance, by strain rods 64 which interconnect the flanges 65, 66 and 61, of which the flanges 65 and 66 are connected to the cylinder 63. for instance, by welding.

Reciprocably mounted in the cylinder 63 is a plunger 68 having a collar 69 en a ing one end of a spring 10, the other end of which is engaged by an adjustable screw or abutment member 1|. The abutment member II is threaded in the flange 61 and may be adjusted from the outside of the accumulator 62; simultaneously, the abutment member II also serves for guiding the left end of the plunger 68.

Packing material I2, compressed by a gland "I3, is provided for preventing leakage around the plunger 68.

The conduit 5| comprises-a check valve 14 and leads to the conduit means I 9 while being connected through conduit [5 with one side of the pump 43. The otherside of the pump 43,

is connected through a conduit 16 with a conduit 11 comprising a check valve 18 and having one end connected to the conduit 5|, while the other end leads to the upper portion of the press cylinder Ill.

Operation It may be assumed that all parts of the hydraulic system occupy the position shown in Figure 1, while the accumulator plunger 68 is in its left hand position so that the accumulator cylinder 63 is loaded with the required quantity of fluid for operation of the servo-motor piston 45.

To perform a working cycle, the operator starts the pump 43 and, in any convenient manner, closes the energizing circuit for the solenoid 25. Energization of the solenoid causes movement of the armature 26 so that the latter causes shifting movement of the three arm lever 28 in clockwise direction whereby the link system 3'! moves the valve member 36 toward the right. This causes the piston 46 to compress the spring 44 and to establish fluid connection between the right hand portion of the bore 59 and the left hand portion thereof through the passageways 58 and bore 4|.

As a result thereof, the spring 10 presses the plunger 68 toward the right so that the fluid in the accumulator 62 passes through conduit 50,

- passageways 56 and bore 4| toward the left hand end of the bore 59 where it acts upon the piston portion 52 so as to move the same and, thereby, the flow control rod 42 toward the right. This results in a shifting movement of the pump 43 to full delivery forward stroke position. Consequently, pressure fluid from the pump 43 is now conveyed through conduits l6 and 11 into the upper portion of the press cylinder l6, while fluid is withdrawn from the lower portion of the press cylinder l9 through conduits 5| and 15.

The ram now moves downwardly by gravity as fast as fluid is withdrawn from the lower portion of the press cylinder I6. During this I movement, fluid passes from the tank I 5 through the surge valve As soon as the ram encounters resistance exerted by a work piece, pressure begins to build up in the upper portion of the press cylinder and closes the surge valve IT. The ram now starts its actual pressing stroke.

A portion of the fluid delivered by the pump 43 through the conduit 16 passes through check valve 18 and conduit 5| into the cylinder 63 of the accumulator 62 so as to move the plunger 68 toward the left until the compressed spring 16 balances the pressure acting on the plunger 68, at which time the accumulator 62 is again loaded When, at the end of the pressing stroke, a

predetermined pressure has built up in the upper portion of the press cylinder In, this pressure is conveyed through conduit 23 to the tonnage control valve 24 so as to cause the latter to interrupt the energizing circuit for the solenoid 25. The thus caused deenergization of the solenoid -25 allows the spring 44 in the servomotor casing 46 to shift the control piston 40 toward the "fluid'from the accumulator 62' to flow through 'conduit 50 to the right hand end of the bore 59 where it acts upon the piston portion 52 so as to move the latter and, therefore, also the flow. control member 42 toward the left.

As a result thereof, the pump 3 is shifted to full delivery retraction stroke position. The pump as now delivers pressure fluid through conduits 15, 5| and I9 to the lower portion of the press cylinder Ill, while fluid is withdrawn from the upper portion of the press cylinder l through conduits l1 and 16 as soon as the pressure in the upper portion of the press cylinder III has been released by the main cylinder release and pump by-pass valve 16. The pressure in the conduit l9 also causes the surge valve I1 to open so that a part of the fluid expelled by the ram I I is passed into the tank I5. The ram ll now moves upwardly.

A portion of the pressure fluid delivered by the pump 43 into the conduit is conveyed through check valve 14 into the cylinder 63 of the accumulator 62 where it moves the plunger 68 toward the left and compresses the spring in the manner previously mentioned.

When the ram ll approaches the end of its retraction stroke, the platen 33 engages the col iar 32 and lifts the push rod 3| so as to cause the collar 30 on the push rod 3| to shift the three arm lever 23 in clockwise direction to such an extent that the latter, by means of the link system 31,

forces the valve member 38 and, thereby, the;

piston 40 toward the right through a partial stroke. This causes a portion of the fluid in the accumulator B2 to pass through the conduit and passageways 58 into the left portion of the bore 59 where it shifts the piston portion 52 and,

thereby, the control rod 42 toward the right until,

the passageways are again closed by the control-- piston 40. The pump 43 is now in substantially neutral or no delivery position, so that the ram ii is halted. The press is now ready for a new cycle.

If, for some reason, the pump 43 with servomotor 46 is to be replaced by a pump and servo:

motor of different capacity, the accumulator 62- can be adapted to the new requirement without any changes in structure and operation. All that is necessary to meet the new situation is merely to adjust the abutment screw H to vary the thrust of the spring Hi. This constitutes a further material simplification over the heretofore known practice of using pilot pumps'which, in order to allow a similar exchange of the main pump, would have to be unnecessarily large, with a corresponding waste in cost and operation.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a hydraulic system, a variable delivery pump, fluid operable servomotor means including a diiferential plunger associated with said pump for controlling the delivery thereof, spring-loaded fluid pressure storage means in continuous fluid communication with one side of said differential plunger and operable to convey fluid pressure to said servomotor means to actuate the latter,

means responsive to a. predetermined pressure at the pressure side of said pump to convey fluid pressure from said pressure side to said storage means for loading the same, and conduit means connecting the interior of said storage means to the discharge side of said variable delivery pump.

2. In a hydraulic system, a pressure fluid source, fluid operable servomotor including a differential plunger operatively connected with said fluid source for controlling the delivery thereof, fluid pressure storage means in continuous fluid communication with the smaller area of said plunger means and operable to convey fluid pressure to the larger area of said plunger to actuate the same, said fluid pressure storage meanscomprising a cylinder with a plunger reciprocably mounted therein, spring means continuously urging said plunger in one direction, means for adjusting the thrust of said spring means, means responsive to a predetermined pressure of said fluid source to convey fluid pressure from said fluid source to said cylinder for loading the same, and conduit means connecting the interior of the cylinder of said storage means to the discharge side of said variable delivery pump.

3. In a hydraulic system, a pressure fluid source, fluid operable servomotor means including a differential plunger operatively connected with said fluid source for controlling the delivery thereof, fluid pressure storage means continuously hydraulically connected with one side of said plunger and operable to convey fluid pressure to one or both sides of said plunger to actuate said plunger, said fluid pressure storage means comprising a cylinder with a plunger reciprocably mounted therein, spring means continuously urging said plunger in one direction, adjusting means for varying the thrust of said spring means, means responsive to a predetermined pressure of said fluid source to convey fluid pressure from said fluid source to said cylinder for loading the same against the thrust of said spring means, and conduit means connecting the interior of the cylinder of said storage means to the discharge side of said variable delivery pump.

4. In a control system, a reversible variable delivery pump, a control cylinder, a fluid operable differential plunger reciprocable in said cylinder and operatively connected with said pump for controlling the delivery and direction of delivery of said pump, hydraulic pressure storage means including a cylinder, a spring-loaded plunger therein for selectively supplying pressure fluid to one or both sides of said plunger, said storage means being continuously hydraulically connected with the smaller area of said differential plunger, valve means associated with said differential plunger and operable to control the fluid connection between the diflerential areas of 

